From the term rofl (Rolling On the Floor Laughing), roflcopter describes rolling on the floor laughing so hard your legs begin moving, causing your horizontal body to turn in a clockwise (or counterclockwise) motion, much like the rotating blades on a helicopter.

A sexual position. It is performed by the female positioning herself on the floor with her pelvis in the air. The male then proceeds to penetrate her. While inside the male rotates in 360 degrees for some time. If performed correctly this results in an intense orgasmic experience for the female.

Yeah so I hit her with the ROFL Copter and she came all over the place!